Friends say I'm living in the past, recounting carefree days of wearing leisure suits, dancing the Macarena, and running WordPerfect 5.1. Now I can indulge my pathological nostalgia with a virtual machine.

Virtual machine programs enable multiple operating systems to run simultaneously on a single PC. The two most popular are Microsoft Virtual PC and VMware Player. Microsoft's product both creates and runs virtual machines, while VMware Player plays preconfigured virtual machines only. Creating your own VMware virtual machines requires an upgrade to VMware Workstation 6 for Windows ($189 direct). VMware Workstation offers many more features than Virtual PC does, including system-state snapshots and the ability to create an image of another computer on your network. Either is a good choice to begin exploring virtualization.

 Run antiquated versions of Internet Explorer to see how your MySpace page, TypePad blog, or business Web-site customization will look in Grandma's IE 4.

 Keep using that trusty custom application that someone wrote for your small business years ago, while for other things you move up to a flashy new OS.

If these prospects seem even more exciting to you than uncovering your old Superman comics up in the attic, you're in for a treat.

How It's Done with Virtual PC

Three essential parts make up a virtual machine: the application itself, a virtual hard drive, and a virtual machine. The virtual hard drive is really just a file on your physical hard drive, and the virtual machine is a file that contains settings used to run the virtual hard disk and emulate the supporting hardware.

To begin, install Virtual PC and fire it up, then click New on the Console screen. You can typically follow the prompts for the default installation. Use the Virtual Disk Wizard to create a new, blank virtual hard drive as wellthis will not affect anything else on your hard drive. When you finish the installation you're not really done; the new virtual machine will be listed in the Virtual PC Console screen, but it won't yet have an operating system. Select the new virtual machine and click Start, then choose CD | Use Physical Drive and choose the drive in which you've placed the installation CD for the OS you want to install. Now simply follow the same steps you would to install the OS on a physical machine. To install applications, repeat the process, choosing CD | Use Physical Drive and install from application CDs exactly the same way.

When you start, it helps to have a workable, installable copy of the quaint old OS you've chosen as your guest operating systemnot, say, a Windows 98 upgrade disc. Similarly, if you want to create a virtual Windows XP machine to run classic games within Vista, you'll need an actual copy of Windows XP.

Remember, each virtual machine you run claims its own share of RAM and disk space (although Virtual PC takes less than 40MB itself) so you'll have to expect some limits on overall performance.

While you'd probably install the Virtual PC program files on your physical C: drive just as you would any other application, the virtual-machine file and the virtual hard-drive file can be located on an external hard drive just as readily. That way, in a pinch you can even use Virtual PC on a crowded laptop to run space-hogging applications from an external hard drive.

I've also discovered that, even though Microsoft's documentation insists that Virtual PC is supported only as a host on Windows XP Professional and above, I've installed it on Windows XP Home Edition without difficulty. The program bellyaches that it's not running on a "supported" operating system, but it runs nonetheless. How much support does Microsoft give to free applications anyway? Zilch, so it doesn't matter.

How It's Done with VMware

Do you crave the thrill of repeatedly installing strange new operating systems? The fastest method is to download preconfigured virtual hard drives, or Virtual Appliances in VMware parlance. There's a whole raft of 'em, configured to run just about every popular open-source OS, as well as several unpopular ones, at www.vmware.com/appliances. It's pretty simple to run a virtual appliance that you've downloaded; just go to the Home screen in VMware Workstation, choose Open Existing VM or Team, and browse to choose your preferred virtual-machine file. The file extension for a VMware virtual machine file is .VMX. Opening an existing VM automatically launches the boot-up sequence for that particular operating system.

Another approach to adding an operating system is to import an image file in the ISO format. Your virtual machine will read from that file as if it were a physical CD-ROM. Choose New Virtual Machine from the VMware home screen and follow the prompts from there to locate your ISO file. You can find ISO files for most open-source OSs on dozens of open-source fan sites.
After you've installed a virtual machine with an operating system in VMware, you can go on to install and run applications. After that, you can easily "clone" the entire virtual hard drive. That's fine for open-source operating systems, but touchy for operating systems that require a license (Windows, for example). Technically, it's a no-no to run multiple instances of a copyright-protected application without extra licenses, just as it's a no-no to share your MP3 collection with your friends.

Editor's Tip: Explore the Future
If you're the futuristic, Buck Rogers type, virtualization has benefits for you, too. Of course, if you still reference Buck Rogers, you're really not all that futuristic, but you still might want to try a suspicious application before exposing your whole machine to its "benefits," or test a fashionable new Linux distro without having to dedicate a whole partition or even a whole machine (and probably a whole day) to the experiment.

Because VMware is clearly more committed to supporting open-source OSs than Microsoft is (hmm, I wonder why?), I suggest that you try VMware if you're seized with a sudden urge to run Linux.

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